The present invention relates to a binocular telescope with internal focusing, which is equipped with a hollow, double joint bridge which connects the two tubes. The bridge includes a spindle of a focusing element and control elements between the focusing element and the focusing means of the telescope, with the latter being housed in sleeves within the tubes.
Binocular telescopes with internal focusing of this type are generally known. Thus, German DE-OS No. 24 24 792 describes a binocular telescope having a central focusing element which, upon actuation for the purpose of focusing, rotates a spindle provided with threads. The spindle in turn moves a stirrup resting under tension against it, and the ends of the stirrup are coupled with transmission rods. These rods cooperate with the focusing elements, with which they are drivingly interconnected. The adjustment of only one optical system to equalize visual differences between the eyes of a user, the so-called diopter focusing adjustment, is not described in this prior art arrangement. It obviously takes place in the conventional manner, by rotation of a ring located in the ocular, which for the purpose of this adjustment requires special adjusting means, such as worm drives or the like. Because the actual sharp focusing of the binocular telescope is effected by means of an adjusting knob located centrally between the two tubes, whereas the diopter focusing adjustment to equalize differences in visual resolution is accomplished by an ocular ring, actual handling of the binoculars becomes cumbersome. In particular, in the case of persons wearing eyeglasses, touching and thus soiling of the glasses by the fingers due to ocular adjustments frequently cannot be prevented. Furthermore, under certain conditions the presence of a drive on the side of the eyepiece may have detrimental effects on the size and configuration of the binoculars.
A binocular telescope is known from German Pat. No. 22 33 055, in which focusing is accomplished by a focusing lens arranged between the ocular and the objective, which is held in an axially displaceable mounting. No diopter focusing adjustment is possible with this telescope.
Another double telescope with internal focusing is described in German DE-OS No. 23 65 652, in which an ocular lens system is axially displaceable forward and backward for the equalization of visual resolution. During rotation of an external tube of the ocular system of lenses, the distance between the external ocular lens and the inner lens system, and thus the magnification of the image, is not altered and the quality of the image not affected.
Aside from the fact that there is no longer any genuine internal focusing present in this arrangement, the danger of soiling a user's eyeglasses is again present as the result of the diopter focusing adjustment on the ocular side. Furthermore, with the larger eyepiece lenses of telescopes designed for the wearers of eyeglasses, there is frequently not enough space left for the installation of a worm drive on the ocular side.